Electrostatic coating method



E. P. MILLER ELECTROSTATIC COATING METHOD July 2, 1957 2 Sheets-Sheet 1Filed Dec. 16, 1953 Xze Q F/QZ 1 9 v I 2 w k r 2....

INVENTOR. EMER) P. MILLER Altar/rays July 2, 1957 E. 1 MILLERELECTROSTATIC COATING METHOD 2 Sheets-Sheet 2 Filed Dec. 16, 1953JNVENTOR. EMERYP. MIL/g7? BY Mai/147 m A I/orneys United States Patent QELncrnosrArrc COATING Mnrnon Emery Parker Miller, lndianapolis, lind.,assignor to Ransburg Electro-Joating Corp, Indianapolis, ind, a corparation of lndiana Application December 16, 1953, Serial No. 398,524

2. Claims. ((31. 1111-93) This application is a continuation-in-part ofmy prior application Serial No. 194,995, filed November 10, 1950, nowpatent No. 2,741,218, and relates to improvements in methods andapparatus for electrostatically coating articles of manufacture. I

The electrostatic method of applying paint and other coating materials,as practiced in industry for a number of years, involves the productionof a spray of electrically charged coating material particles and theelectrostatic deposition of such charged particles on the articles to becoated. In one rather widely used process, the articles to be coated aremoved successively by a conveyor past a discharge electrode betweenwhich and the articles an electrostatic field is maintained, and a sprayof the coating material is discharged into such field from a spraygunusing a blast of air both as an atomizing medium and as aparticle-transporting medium. Generally speaking, apparatus forpracticing such process has usually been designed so as to minimize asfar as practical the possibility that the air blast would carry thecoating material particles out of the depositing field. With that objectin view, the Ransburg et al. United States Patents Nos. 2,247,963 and2,334,648 proposed arranging tr e spray gun or guns to dischargegenerally parallel to the conveyor, thus reducing the likelihood thatspray particles would be carried through the spaces between articles andtherebeyond out of the field. The generally parallel spray furthertended to insure that the majority of the sprayed particles, when theylost their initial momentum, would still be close to the path followedby the articles and hence would be elfectively subject to the depositingaction of the field.

Where coating with a parallel spray was carried out in a spray boothwhich was exhausted in such a manner as to create an air current movinggenerally parallel to the spray, some of the sprayed particles might becarried for inordinate distances before being deposited. In such asituation, it was proposed (Ransburg et al. Patent No. 2,463,422) tomove the articles over an L-shaped path, to discharge the spray alongone leg of such path toward the other leg, and to place on the remoteside of such other leg an electrode which would cause the relatively fewslowly moving particles passing between articles and approaching it toreverse their direction and be deposited.

While the arrangements above described resulted in substantial savingsof coating material, there were cases in which they left something to bedesired. Thus, with the spray directed generally parallel to the articlepath, some particles were deposited much more quickly than were others,there was considerable variation among the particles in respect to theirdryness at the time of deposit, and it was therefore necessary to use inthe coating material a solvent sufficiently slow to insure that thedriest of the deposited particles would not be too dry. Further, theparallel spray sometimes resulted in an inadequate coating ofarticle-portionswhich were electrically shielded by otherarticle-portions.

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Another expedient for reducing the number of particles carried out ofthe field by their initial momentum is disclosed in Ransburg et al.Patent No. 2,546,701, where the spray gun was arranged to discharge pasta particle-charging discharge electrode perpendicularly to the articlepath. Such a gun, if operated continuously and in fixed position, wouldproject much of the sprayed material through the spaces between articlesand beyond the field; and to prevent such a loss of coating material,the patentees proposed to arrange the gun for manual manipulation andcontrol, so that it would be maintained aimed at a passing article andshut off completely when there was no articles within direct range ofthe spray. This apparatus had advantages over those disclosed in thepatents earlier mentioned in that the particles reached the work atsubstantially the same degree of dryness and in that the gun could be sodirected as to cause coating material particles to be projected ontoelectrically shielded areas under their own momentum; but, because itrequired manual operation of the gun, it entailed relatively high laborcosts.

Ransburg Patent No. 2,5 67,781 discloses a method and apparatus designedto retain the eificiency of electrostatic coating while eliminating handlabor and providing for the projection of coating material ontoelectrically shielded article-portions. While this arrangementeliminated manual gun-manipulation and did provide an adequate coatingon electrically shielded areas, there was still a wide variation in thedryness of the particles at deposition.

it is an object of this invention to produce an electrostatic coatingmethod and apparatus which will in large measure preserve the advantagesand eliminate the disadvantages of the prior systems above described.More specifically, it is an object of the invention to promoteuniformity in the state of dryness of electrostatically depositedcoating material particles, to provide an adequate coating ofelectrically shielded areas, and to preserve the relatively highpaint-utilization efiicienciescharacteristic of prior electrostaticcoating methods such as have been described above. Another object of theinvention is to reduce the floor space required for electrostaticcoating apparatus and to permit the use of paint booths and exhaustsystems of a simple type heretofore used in non-electrostatic coatingmethods.

One feature of the invention is directed to a coating method in which aseriesof articles is conveyed along a predetermined path in spacedrelation to and between two electrodes which are held at a highelectrical potential relative to the articles to ionize and precipitateupon the articles particled coating material from a source directedapproximately normal to said path at the position of closest approach ofthe path to said source and past and along side of one of saidelectrodes toward said articles. The articles are thus presenteddirectly to the spray to collect by mechanical impingement a portion ofthe coating material and are so positioned with respect to theelectrodes as to collect by electrical recipitation particles not soimpinged and other particles which cross the path of travel of thearticles. By thus combining the two coating forces, high coatingelficiencies are obtainable.

Another feature of the invention resides in spacing the articles alongthe path in such a manner that a portion of the coating materialparticles pass between the articles to that side of the article pathwhich is opposite the spray source and will then be reversed by theelectrostatic action of an electrode on that side of the path and beprecipitated upon those surfaces of the articles which are not in facingrelationship to the spray.

A further feature resides in=having the electrode adjacentythe spraysource composed of at least two parts, one

:3 on either side of said spray, so that the spray in moving toward thearticle passes between and comes under the charging influence of one orthe other of these parts. A similar multi-part electrode can be placedon the side of the article path remote from the spray source toprecipitate particles moving through the spaces between articles.

The invention further contemplates that the spray source can bereciprocated or oscillated about a mean position so that the bulk of theissued coating material will impinge directly upon the article as itmoves along its predetermined path. In addition it contemplates that theelectrode might also be similarly oscillated -or reciprocated incoordination with the spray source.

In all the above features it is contemplated that the coating materialwill be directed toward the article path in a direction which isapproximately normal to the path. It is further contemplated that thisdirection will be generally normal at the position of closest approachof the path to the source of the spray of coating material. In this waythe material will be initially applied to the article by mechanicalforces directly from the spray sources and by electrical forces on bothsides of the path as soon as possible after leaving the atomizer and thetendency will be to have a full wet coat of material built up on thearticle promptly.

This quick formation of a wet coat is advantageous over normalelectrostatic methods since it permits the coating material to beformulated with faster solvents and thus overall drying requirements arereduced.

While in certain of its aspects the invention contemplates that thespray source directs coating material toward the articles over a pathwhich is alongside of but still in particle-charging relation to theelectrode, it is preferable that the electrode not be exposed to thedirect blast of the Wet spray particles from a closely positioned sourceso that the electrode will not accumulate by direct impingement coatingmaterial which later under the influence of the field will string offand be carried to the parts as objectionable slugs.

These and other features of the invention will be made apparent from thefollowing specifications and claims.

In the accompanying drawings:

Fig. 1 is a plan view of one embodiment of the invention as used forfinishing index tabs and is taken along line 11 of Fig. 2,

Fig. 2 is a side elevation of the apparatus of Fig. 1,

Fig. 3 is an isometric view of the rack used to hold the tabs during thepainting operation,

Fig. 4 is a plan view of another embodiment of the invention in whichelongated cylindrical articles arranged in clusters are coated,

Fig. 5 is a partial elevation taken along line 55 of Fig. 4,

Fig. 6 is a front view of apparatus embodying another modification ofthe invention as incorporated with an overhead conveyor, and

Fig. 7 is a plan view of a modification of the invention in which thespray gun is moved simultaneously with one of the electrodes.

As illustrating one modification of the invention, there is shown inplan view in Fig. 1 and in side elevation in Fig. 2 a spray booth 10having an open side 11 and an exhaust plenum 12 which is" connected toexhaust duct 13. Passing through this both from one side to the other isa conveyor 14 to which are attached frames 15 holding the articles 16 tobe coated. These frames as shown in detail in Fig. 3 have a series ofwires 17 stretched across them and have two attachment members 18 bywhich they a are supported from the conveyor. The articles 16, hereshown as metal index card tabs, are supported saddlewise on these wires,one next to another, on all wires. The frame can be filled or not asdesired. These frames are supported on the conveyor and carried by itthrough the spray booth in the direction of the arrows 19 in Fig. 1. Inthe booth, on one side of the conveyor and spaced from it, is located anelectrode 20 comprised of conducting frame 21 which serves to supportunder tension the charging or ionizing elements 22. A similar electrode23 may be positioned on the opposite side of the conveyor from electrode20. These two electrodes, by conductors 24 and 25, are electricallyconnected to each other and to the one terminal of a high voltage source26 whose other terminal is grounded as at 27. Since the conveyor, thecarrying frames, and the articles on the frames are all electricallyconnected, grounding the conveyor as at 28 serves to ground the articlesto be coated.

Under this arrangement an electrostatic field is established between theelectrodes and the articles when the source of high voltage isenergized. The gradient of this field is high adjacent the electrodes 20and 23 because of the nature of the ionizing elements and thus anyparticles in their vicinity will become charged and be repelled by thefield toward the articles which are connected to the other terminal.

Coating material in finely atomized form is introduced into this fieldfrom outside by an atomizing device 29 positioned to direct the spraypast and adjacent electrode 20 into the field and generally normal tothe path of travel of the conveyor at the position of closest approachof the articles to the gun. As the articles 16 are carried through thespray booth their front side 30 is thus subject to and receives coatingmaterial from the direct mechanical impingement action of the spray aswell as from the precipitating action of the field. They also receive ontheir front sides material which has become charged by passing the frontelectrode but which has escaped being attached to the article because ofair bounce or turbulence. Such particles, after bouncing off thearticle, are reversed again and urged toward the articles by the actionof thc field. Still other particles from the atomizer 29 will passbetween the articles on the frame and enter the field between the backside of the articles and the second electrode 23. Under the action ofthis field most of these particles will have their direction reversedand will be returned to the articles to supply the coating on their backside. This phenomenon of material being redirected to coat surfaces notin the direct impingement pattern of the atomizer is referred to as wraparound and accounts in a large measure for the added etficienciesobtained by the method of this invention. Lateral surfaces, such as thesheared edges of the tabs shown herein, are also coated by this action.Any coating material particles escaping these multiple forces ofprecipitation are carried with the evaporating solvent fumes into theplenum 12 by the exhaust.

This method is particularly suited for finishing this article since itis desirable that the inside surface of the back leg of the tabimmediately behind the tab window 31 be coated to present a goodappearance when a legend card is not in the tab. The direct action ofthe atomizer acting on the front of the tab carries coating material tothis area through the window opening while the overspray coats theremaining portions of the article. One atomizing unit thus suflices todo the complete operation. By mechanical spraying alone, three atomizersare needed for this same coating operation.

If it is desired to increase the area of the support frame and thusincrease the number of articles which can be sprayed per foot ofconveyor, the atomizer can be moved up and down in a plane parallel tothe plane of the article support frame and thus distribute its materialover a larger area than is permitted by a simple divergence of the spraypattern.

Another modification of the invention is shown in plan view in Fig. 4and further detailed in Fig. 5 which is a partial elevation along lines5-5 of Fig. 4. In this modification a spray booth 100, which may be of atype commonly used in non-electrostatic spray painting, is arranged withan open face 101 opposite an exhaust plenum 102. A floor supportedconveyor 103 enters one side of this awe -s i booth, passes through thebooth, andenierges through the other side. The conveyor-carries a seriesof upwardly projecting spindles 104 each shown as adapted to support anannular series of vertically disposed, generally cylindrical articles105, which might be cartridge tanks. Preferably, the spindles 104 arerotatably mounted on the conveyor and means such as a stationaryfriction bar 106 engaging with rotator wheels 107 on the spindles isprovided for rotating the clusters of articles 105-as they pass throughthe booth. Between the open side 101 of the booth and the path followedby the articles I provide a plurality of vertically extending dischargeelectrodes 110, preferably fine wires, supported from insulators 111 inhorizontally spaced relation in a plane parallel to the article path. Asimilar set of electrodes 112 is arranged on the opposite side of thearticle path.

Supported in fixed position outwardly beyond the elec trodes 110 is aspray gun 115 oriented to discharge generally horizontally and directlytoward-i. e., substantially perpendicular to-the article path. Thisspray gun, which is capable in itself of projecting atomized coatingmaterial particles well beyond the article path, is conveniently of thetype employing compressed air as an atomizing and particle-transportingagent. The gun is located to discharge between two of the electrodeelements 110, and such elements are spaced far enough apart to be out ofthe spray projected from the gun.

The electrodes 110 and 112 are connected in common to a terminal of ahigh voltage source 117 the other terminal of which is grounded; and asthe articles 105 will be grounded through the conveyor, an electrostaticfield will exist between the articles on the one hand and the electrodeson the other. The particles of coating material passing betweenelectrodes 110 will be electrically charged and urged toward depositionon the articles by the electrostatic forces of the field. Many of theparticles will escape deposition initially and will .be carried by theirpreserved initial momentum across the article path, but such particleswill be repelled, reversed and redirected toward the articles by theelectrodes 112. It is possible that some particles passing-close to thearticles but escaping deposition thereon will suffer a loss ordiminution of their charges; but since the atmosphere around theelectrodes 112 will be ionized, such particles will be quickly rechargedand made subject to the repelling effect of those electrodes.

As will be obvious, the space within a cluster of articles 105 will berather effectively shielded electrically, and any electrostaticdepositing effect in such space will be relatively weak. Nevertheless, asubstantial number of the coating material particlessvill .be carried bytheir own momentum into ,andacross the interior of the cluster toimpinge on the inner surfacesof articles on the remote side of thecluster, and thus all portions of the surface of each article may beadequately coated. If the particles possessed less momentum, the fieldwould be more effective in deflecting them from their original course;and as the field is much stronger over the'exterior of the cluster thanwithin it, the outwardly presented surfaces of the articles wouldreceive a heavier coat and the inwardly presented surfaces a lightercoat.

The articles 105 are shown as provided at their ends with annular beadsor heads 105'. The corners at the bases of such beads are electricallyshielded and hence tend to receive a relatively light coat ofelectrostatically deposited material. However, by my invention, the samehigh momentum which causes some of the spray to be deposited on thesurfaces presented inwardly of the articlecluster causes other particlesto be projected on to the electrically shielded areas at the base of thebeads.

Fig. 6 illustrates another modification of the invention. In thisdrawing, which is a front view of the apparatus, a conveyor 200 carriesarticles 201 into and through a spray booth 202. The front of the boothis open and at 6 its rear jthere is an' exhaust plenum (not shown). Theconveyor enters the side of the booth, turns andtravels away fromexhaust plenum toward the front of the booth. Articles .201, indicatedhere as external jackets for Water heaters, are supported from theconveyor by hanger 203 and are carried by it through the booth.

In the booth, on both sides of the conveyor, there is an oscillatingmechanism 204 which carries a spray gun 205 and an electrode element 206in spaced relation to the article surface. The electrode is supported byinsulator 207 which serves to isolate it from the oscillating mechanismso it can be connected to one terminal of a high voltage source 208 byspring connection 209 and conductor 210. By means of this source theelectrode is maintained at a high electrical potential with respect tothe article which is grounded as at 211 and a field therefore existsbetween them which has a gradient capable of charging particles adjacentthe electrode.

A spray of coating material is introduced past the electrodes by thespray gun 205-and travels essentially normal to the article. Beingcharged by proximity to the electrode, it is then put onto the articlesurface by the combined mechanical action of the spray and theelectro-depositing action of the electrostatic field.

To obtain distribution over the article surface, the oscillator 204 iscaused to move the electrode and spray gun up and down in a verticalplane parallel to the article surface between the extreme positions ofthe gun and electrode shown in dotted lines and as indicated by thearrows 212.

With this arrangementa single gun and electrode assembly on each side ofan article can be used to simultaneously and efficiently coat oppositesides of single articles. If the object is cylindrical it can be rotated'while passing the gun stations to have its entire surface coated or, ifit is rectangular, it can be indexed and carried past another similarstation to have its other two sides finished. The exhaust air movingparallel to the path of conveyor travel serves to carry away evaporatingsolvent fumes and any material which might escape deposition.

Fig. 7 illustrates in plan view' another modification in which articles300 move along a conveyor, illustrated by line 301, past and betweenfixed electrodes 302 and movable electrode 303, a spray gun 304, movablewith and mounted on the same support mechanism 305 as are electrodes303, is arranged to be turned off and on by the action ofswitches306.and 307. It is aimed to direct a spray of coating material'between thetwo electrodes 303 toward and normal to the path of travel of articles300.

In operation switch. 307 is tripped by an object supporting spindle onthe conveyor as the conveyor moves in the direction of arrow 314 andturns on the spray from gun 304 when the gun is aimed directly at apreceding article on the conveyor. By an arrangement not shown, supportmechanism, 305 is. arranged to move parallel to andin step withconveyor301 when switch 307. is tripped. It continues this motion and the guncontinues to spray until switch 306 is activated, at which time the gunis turned 0E and the support 305 returns rapidly to its originalposition. The cycle is repeated when switch 307 is again tripped by thefollowing spindle. By this arrangement the spray gun and theprecipitating electrode 303 are moved with the conveyor from theposition shown in full lines to the position shown in dotted lines whilethe spray is activated and directed for normal impingement upon anarticle and they return to their original position past the spacesbetween the articles with the spray turned off.

The detailed characteristics of the apparatus may vary to suitcircumstances. In general, I have found it convenient to maintain anaverage potential gradient of 8,000 to 10,000 volts per inch between theelectrodes and the articles. For most work, a distance of about teninches between the articles and electrodes charged to 90,000 volts willbe satisfactory. The space between adjacent nes of the electrodeelements, such as the wires 110 and 112 of Figs. 4 and 5, preferablyapproximates their distance from the work. The electrodes desirablyextend for some distance above and below the tops and bottoms of thework, and both series of electrodes desirably extends along the articlepath to, or even beyond, the limits of the billowing spray dischargedfrom the spray gun.

While I have shown all the electrodes as discharge electrodes capable ofionizing the adjacent atmosphere, it may be noted that the electrode onthe remote side of the work from the spray gun may be non-ionizing.Ionizing electrodes on both sides of the article path are preferred,however, because of their capability of charging or rccharging thecoating material particles which approach them.

From the above described modifications it will he evident that theinvention allows added efficiencies of coating application to beobtained by combining in a parallel manner the mechanical action of aspray jet and the precipitating action of an electrostatic field. It isalso apparent that surfaces facing the atomizer, as well as those notfacing it, can be coated simultaneously and that the particles will allbe deposited promptly and with substantially the same degree of dryness.Because of this prompt deposit of all particles, it is possible to userelatively volatile solvents for the coating material, thus reducing thetime required to dry the finished coating.

I claim:

1. A method of electrostatically coating articles each having anelectrostatically shieldable portion of relatively large area and,spaced from said shieldable portion, an electrostatically shieldingportion of smaller area, comprising moving the articles over a fixedpredetermined path past and in spaced relation to electrodes located infacing relationship on opposite sides of the article path, one of whichelectrodes is of ionizing character, maintaining the articles as theypass between said electrodes so oriented that the shielding portion ofeach article is disposed between the shieldable portion and saidionizing electrode whereby said shieldable portion becomeselectrostatically shielded, forming at a point on the opposite side ofsaid ionizing electrode from said path a spray of finely divided liquidcoating material, maintaining a high difference of electrical potentialbetween said electrodes and articles to create an electrostatic fieldbetween the electrodes and the articles, with said field creating anelectrostatic shield over said shieldable portion of an article,propelling said spray approximately normal to said path at the positionof closest approach of the path to said formation point toward both saidelectrodes and past, and in particle charging proximity to said ionizingelectrode to cause particles passing the ionizing electrode to acquirean electric charge opposite in sign to that of the articles and therebyto cause a portion of the spray to be electrostatically deposited onarticle surfaces presented toward said ionizing electrode, with anotherportion of said spray being propelled toward at least a part of saidshielded portion and past said shielding portion with a velocitysufficient to cause deposition on such part of said shielded portion ofthe last mentioned portion of the spray in spite of the existence ofsaid electrostatic shield, said articles being spaced apart to permit afurther portion of the spray to enter the space between the articles andbecome electrostatically deposited on article surfaces presented towardssaid other electrode, with all of the portions of the spray beingdeposited substantially simultaneously to prevent excessive drying ofany of said portions.

2. A method of electrostatically coating articles each having anelectrostatically shieldable portion of relatively large area and,spaced from said shieldable portion, an electrostatically shieldingportion of smaller area, comprising moving the articles over a fixedpredetermined path past and in spaced relation to an electrode ofionizing character located on one side of the article path, maintainingthe articles as they pass between said electrodes so oriented that theshielding portion of each article is disposed between the shieldableportion and said ionizing electrode whereby said shieldable portionbecomes electrostatically shielded, forming at a point on the oppositeside of said path from said electrode a spray of finely dividedelectrostatically charged liquid coating material, maintaining a highdifference of electrical potential between said electrode and thearticles to create an electrostatic field between the electrode and thearticles, with said field creating an electrostatic shield over saidshieldable portion of an article, propelling said spray toward saidarticles and electrode in a direction approximately normal to said pathat the position of closest approach of the path to said formation pointthereby to cause a portion of the spray to be electrostatically chargedand deposited on article surfaces presented toward said spray, .withanother portion of said spray being charged and propelled toward atleast a part of said shielded portion and past said shielding portionwith a velocity sufficient to cause deposition on such part of theshielded portion of the last mentioned portion of the spray in spite ofthe existence of said electrostatic shield, said articles being spacedapart to permit a further portion of the spray to enter the spacebetween articles and become electrostatically deposited on articlesurfaces not presented to wards said electrode, with all of the portionsof the spray being deposited substantially simultaneously to preventexcessive drying of any of said portions.

References Cited in the file of this patent UNITED STATES PATENTS1,855,869 Pugh Apr. 26, 1932 2,221,338 Wintermate Nov. 12, 19402,270,341 Ransburg Jan. 20, 1942 2,476,145 Gwyn July 12, 1949 2,677,626Bodle May 6, 1954 FOREIGN PATENTS 591,474 Great Britain of 1947 599,466Great Britain of 1948

1. A METHOD OF ELECTROSTATICALLY COATING ARTICLES EACH HAVING ANELECTROSTATICALLY SHIELDABLE PORTION OF RELATIVELY LARGE AREA AND,SPACED FROM SAID SHIELDABLE PORTION, AN ELECTROSTATICALLY SHIELDINGPORTION OF SMALLER AREA, COMPRISING MOVING THE ARTICLES OVER A FIXEDPREDETERMINED PATH PAST AND IN SPACED RELATION TO ELECTRODES LOCATED INFACING RELATIONSHIP ON OPPOSITE SIDES OF THE ARTICLE PATH, ONE OF WHICHELECTRODES IS OF IONIZING CHARACTER, MAINTAINING THE ARTICLES AS THEYPASS BETWEEN SAID ELECTRODES SO ORIENTED THAT THE SHIELDING PORTION OFEACH ARTICLE IS DISPOSED BETWEEN THE SHIELDABLE PORTION AND SAIDIONIZING ELECTRODE WHEREBY SAID SHIELDABLE PORTION BECOMESELECTROSTATICALLY SHIELDED, FORMING AT A POINT ON THE OPPOSITE SIDE OFSAID IONIZING ELECTRODE FROM SAID PATH A SPRAY OF FINELY DIVIDED LIQUIDCOATING MATERIAL, MAINTAINING A HIGH DIFFERENCE OF ELECTRICAL POTENTIALBETWEEN SAID ELECTRODES AND ARTICLES TO CREATE AN ELECTROSTATIC FIELDBETWEEN THE ELECTRODES AND THE ARTICLES, WITH SAID FIELD CREATING ANELECTROSTATIC SHIELD OVER SAID SHIELDABLE PORTION OF AN ARTICLE,PROPELLING SAID SPRAY APPROXIMATELY NORMAL TO SAID PATH AT THE POSITIONOF CLOSEST APPROACH OF THE PATH TO SAID FORMATION POINT TOWARD BOTH SAIDELECTRODES AND PAST, AND IN PARTICLE CHARGING PROXIMITY TO SAID IONIZINGELECTRODE TO CAUSE PARTICLES PASSING THE IONIZING ELECTRODE TO ACQUIREAN ELECTRIC CHARGE OPPOSITE IN SIGN TO THAT OF THE ARTICLES AND THEREBYTO CAUSE A PORTION OF THE SPRAY TO BE ELECTROSTATICALLY DEPOSITED ONARTICLE SURFACES PRESENTED TOWARD SAID IONIZING ELECTRODE, WITHIONANOTHER PORTION OF SAID SPRAY BEING PROPELLED TOWARD AT LEAST A PART OFSAID SHIELDED PORTION AND PAST SAID SHIELDING PORTION WITH A VELOCITYSUFFICIENT TO CAUSE DEPOSITION ON SUCH PART OF SAID SHIELDED PORTION OFTHE LAST MENTIONED PORTION OF THE SPRAY IN SPITE OF THE EXISTENCE OFSAID ELECTROSTATIC SHIELD, SAID ARTICLES BEING SPACED APART TO PERMIT AFURTHER PORTION OF THE SPRAY TO ENTER THE SPACE BETWEENON THE ARTICLESAND BECOME ELECTROSTATICALLY DEPOSITED ON ARTICLES SURFACES PRESENTEDTOWARDS SAID OTHER ELECTRODEBWITH ALL OF THE PORTIONS OF THE SPRAY BEINGDEPOSITED SUBSTANTIALLY SIMULTANEOUSLY TO PREVENT EXCESSIVE DRYING OFANY OF SAID PORTIONS.